Patients increasingly survive critical care, but for many the experience is psychologically tormenting in part because they lose all control over their environment. Patients with neurological injury in particular suffer from this major loss of autonomy which impacts their long term recovery. Brain-computer interface (BCI) technology transforms physiological changes associated with patient thoughts into actionable outputs. The technology is rapidly advancing and well established outside of the critical care setting. The goal of this project is to determine whether conscious and unconscious appearing ICU patients are able to communicate their basic needs, such as pain, hunger, and thirst, to health care providers using the BCI technology. We will apply a bedside BCI system in the ICU using a machine-learning algorithm that analyzes changes in routine EEG in response to standardized questions presented to the patient by headphones. The BCI system will provide immediate closed- loop feedback (auditory and/or visual) to patients about their performance. To achieve our goals, we will first test if conscious ICU patients are able to express basic needs, such as pain, to health care providers using the BCI technology. Patients will trigger the BCI system to then express their needs in response to specific questions (e.g., ?Do you have pain??). Secondly, we will determine whether basic communication is possible for patients with cognitive motor dissociation (i.e., patients who appear unconscious, but follow commands using EEG motor imagery paradigms). We will test if these patients are able to use the BCI system to respond to simple questions (i.e., ?Activate the alarm?). Finally, we will assess the patient's experience using BCI technology as part of this study, as well as acceptance of using BCI technology in future clinical trials from patients, families, and health care providers involved in the study. The long-term goal of this proposal is to prepare a large clinical trial to test the benefits of BCI-assisted communication in brain-injured ICU patients.